Taranis,
The problem is that you can't keep the current aircraft. There are acute obsolescence problems with the legacy aircraft which would render it either horrifically expensive to support or unflyable. The aircraft would also become increasingly incapable of either interaction with allies, or protecting itself against threats. High utilisation Ops in Afghan have robbed years off the fleet - this is the consequence of "surging" for nearly a decade.
V-22 is a great aircraft at niche roles, but I doubt many in the Army/RM would trade Apache fire support for a ride in an Osprey. CHF should have had V-22 over Merlin, but that would have been politically impossible.