Yeah, albeit I'm not sure about the effective date. It was supposed to be from the end of the original contract, but there's nothing specifically about an extension signed 6 months earlier.
One way or another, from July the new wage would count completely towards the cap, so someone on 5k today, who is currently only counting 1.8k towards the cap, would count 5k if they signed a contract extension.
I did a quick calculation and I think we're at around £1.9m from our current first team squad, but that's with the legacy contracts being counted at 1.8k a week rather than their true cost. That gives us around £11k a week to play with, but that needs to extend so many players that it's tough to see how it happens. For example, if all of the 19 current over 21's in the squad were willing to accept £2.5k a week, that's an extra £700 per player, which costs £13.3k a week. On that basis, there can be no glamour signings over the age of 21 or not on loan.
Tough to see a way round it without promotion. It should be proportional to the income of the club.