News that the proposed inner Thames Estuary airport has been dropped from the UK Airports Commission's shortlist has surprised nobody, as the decision was foreshadowed in the body's interim report in December last year.

It is looking increasingly likely that the Commission's recommendation will be for a third runway at London Heathrow airport and a second at London Gatwick. Meanwhile, London Mayor Boris Johnson's rising political star will ensure that the estuary airport plan – which he enthusiastically backs – will be resurrected in due course.

The only options remaining on the Commission's shortlist are extra runways at Heathrow and/or Gatwick. The conclusions and recommendations will not be presented to government until after next year's general election – a carefully choreographed arrangement reflecting the political difficulty of the decision.

In a tacit recognition that there is no alternative to increasing runway capacity in the London area, the present prime minister David Cameron says if his Conservative Party is elected, it will accept the Commission's recommendation, whatever it is.

The reasons for the Commission's decision to drop the estuary airport plan are many, but the essential issue is summed up in seven key words in the Commission's announcement: "The need for additional capacity is urgent." The Thames estuary airport project – nicknamed "Boris Island", because Johnson has long backed it – would take far longer than any other solution to deliver. Commission chairman Howard Davies, however, also makes much of the massive cost of constructing the airport and providing supporting ground transport infrastructure at a virgin site – the latter involving substantial cost to the public purse.

Johnson reacted predictably to the news, telling The Guardian: "In one myopic stroke the Airports Commission has set the debate back by half a century and consigned their work to the long list of vertically filed reports on aviation expansion that are gathering dust on a shelf in Whitehall."

The mayor maintains a runway at Gatwick would only be a short-term solution, while expansion at Heathrow would be politically impossible and environmentally disastrous, because the additional noise and pollution will affect many more people than anywhere else.

Air-quality monitoring shows the Heathrow area already often fails to meet standards – or only marginally achieves them – so the future is dependent upon more efficient aircraft engines and better air traffic management. Ironically, however, the chief executive of UK air navigation service provider NATS, Richard Deakin, has pointed out that Heathrow expansion enables the most efficient overall ATM system for the UK southeast, and is therefore the lowest emission solution viewed nationally rather than locally.

Meanwhile, Johnson – now accepted by the Conservatives to stand as a candidate for election as a member of parliament in a safe West London seat – has no intention of fading away politically, nor of dropping his estuary airport plan. It will remain a high-profile subject for continued debate, even when the Airports Commission's final recommendation is published.

Johnson's only concession to recent developments has been to drop his proposal that Heathrow should be closed when Boris Island is up and running, and that it would instead become "an Orly" for London. This reference to Paris's downtown airport Orly is Johnson's concession to the unpopularity of a Heathrow closure in his promised West London constituency, where the airport is by far the largest local jobs provider.

With Johnson now clearly set to be a Conservative big-hitter – and possible leader – the Boris Island airport solution for London is alive and well for the future. However, in the meantime a quick solution is required.

Remaining on chairman Davies' shortlist are two alternatives at Heathrow: a new runway to the northwest, or a major continuation of the existing north runway to the west – enabling it to operate as two runways – and one option for Gatwick, namely a new runway to the south of the present one.

In 2010, Flightglobal opined that, regardless of whether a third runway should happen, it would. In March 2012 – nine months before the Airports Commission was set up – another Flightglobal comment piece noted: "The option of a third runway at Heathrow is still there, looming dangerously, because it is the quickest, cheapest workable solution to London's increasingly dire runway-capacity shortage.

"The longer the government dithers, the more attractive the third runway option will become, until it becomes completely inevitable."

The Commission says: "While we recognise the need for a hub airport, we believe this should be a part of an effective system of competing airports to meet the needs of a widely spread and diverse market like London's."

So, unless the Commission changes its mind as the result of further deliberations between now and summer 2015, it seems likely that its recommendation will be one of the new Heathrow runways, plus a Gatwick south runway a few years later.