Nor do I ever recollect a situation where a Warrior had to wait for the MBTs to catch up, something to do with all arms groupings. Even on an objective Warrior was protected by the accompanying tanks, the clue was in the name Intimate Support.
Do the tactical arguments no longer apply? Can intimate support no longer be done? Or is the Warrior upgrade not going to incorporate a stabilised weapon system?
Reliance on intimate support is still a comparative reduction in capability, in two respects.
Firstly, in terms of reaction to new targets. If the opposition is co-operative enough to place his defenses sufficiently in the open that the overwatching tanks can deal with them, then that's fine, but if they decide they're going to use terrain masking or whatever, then it may well be the case that the only allied vehicle with line of sight to the threat is the IFV. Even if it isn't a matter of line of sight, it may just be that the IFV spots the threat first. They have a bunch of eyeballs scanning around, I would think that a company of IFVs would have a reasonable chance of spotting things before the accompanying platoon of tanks did. At which point you have to hand off the target, or the IFV has to deal with the problem itself, whichever is faster. You can try bringing the tanks up close with the IFVs, but then they no longer are a detached support-by-fire element able to deal with things like "unexpected counter-attack from the flank" (and may also put tanks at greater vulnerability). It would require yet another group of tanks to be added to the attack.
The other issue is the amount of targets which can be engaged at once. If an infantry company is moving forward, that's, what, a dozen cannon or machinegun not doing anything in the most critical and vulnerable phase of the assault? Even if you assume an equal number of tanks to IFVs, you're only OK if the number of targets does not exceed more than half the number of attacking vehicles. I should say that 'targets' can mean not only identified targets, but suspicious bushes, ditches, etc in which an as-yet unidentified threat may lurk and require either preventative suppression or a rapid kill. The only counter to this is to add more vehicles to any assault, but the British Army is running short on vehicles lately, it seems.
The only significant downside to a stabilised gun on an IFV is cost. The British may have considered it, in advance, to be a 'nice to have', but it adds a lot of flexibility for not very much cost.
This is, of course, a separate issue to choosing a clip-fed weapon.