You've got more chance of plaiting snot.
The Army has nearly three times the manpower of the RAF.
The RAF has about 40 active, non-training stations, but only about a third of those are flying stations.
The Army has about 130 non-training regular Major units (i.e. regimental size, approx 650 people).
RN could, has, and will, run an FJ fleet or two. They're also taking Merlin. The Andrew need both AD and CAS types. Why couldn't they do it all? They already have the strategic role (nuc and TLAM).
The Army runs as many helos as the RAF. Chinooks elsewhere in the world are run by their armies. The Army has a Really Large logistics Corps. What are AT assets if not flying trucks and buses? The Voyagers are run on contract anyway.
It would be far, far, easier to return to the RFC and RNAS than to have the Army's role subsumed by the RM and RAF. The RAF Regt doesn't even have Rapier or tracks anymore.
Air Marshals keep getting out-flanked by Generals and Admirals in spending rounds.
The Army is the RAF's major "customer". CAS, tactical bombing, AT and SH are nearly all in support of the Army.
Currently, AD (both ground and air) are about the only thing that the RAF does for itself (i.e. "air power").
If there's a Service to be lost, it won't be the Navy or the Army. But I do hope the RAF makes it.