Leaf... of course that is relevant to those already in the system, it's the only metric we have to go on. There's no other way to go on... weekly polls of who's planning on leaving/retiring? I would have answered differently on almost every poll.
When NZ 737 (soon) and VARA commands (not so soon) come into seniority system play the picture will only become less clear. That doesn't mean "today's time to command" isn't a valid metric to those contemplating joining the greater VA group.
Over the next couple of years whether VA is expanding, contracting or neither is difficult to judge, tbh. Are we talking capacity (ASK)? Probably slightly up. Hours flown? Down. Movement through the ranks? Massive. Compounded by drawing E190 and ATR pilots into Boeings as fast as simulator constraints allow. VA is opaque. 2 737s mothballed in Mel (one getting some attention this week), one delivered, E Jets leaving, possibly unrealistic flying scheduled for just 6 ATRs and the constantly varying Alliance capacity leased in. One 777 captain leaves and there's years of training required to move the 5 (minimum) seat/fleet changes that drives.