But what is a "gap"? Like you said, you don't expect any major air battles anytime soon. It seems to me a gap is a construct used by our various defense departments and industries to build new and more expensive stuff. Nothing wrong with using current airframes or even bringing back old ones like the US has done with the OV-10.
I'd say the Royal Navy having to wait until 2020 (expected timeline as of now) to regain the ability it lost 6 years ago (IIRC) of operating combat aircraft from their naval carrier(s), when it is deemed core to their strategy and had actually seen use in one of their not so far off major conventional engagements, is a real gap in their capabilities and their ability to project force. I believe the RAF may reach historic lows in combat aircraft numbers in coming years until being delivered their F35, as well.
And while there's maybe no major air battle to be fought anytime soon, bombing campaigns involving key European armies will certainly continue to be a thing for a fair number of years and require to have enough airframes to be able to conduct them while doing all the usual missions of home defence. Considering the uncertainty of the upcoming US administration's commitment to NATO and as a Frenchman, I'd be more at ease with a key defence partner regaining some of that capacity sooner than later instead of relying on the kindness of strangers should a crisis erupt.
I know the delays and cost have stirred up controversy in Israël, Australia, Canada or Australia, but I'm less familiar with their Air Force needs which are probably not as urgent as those of the British.
