Anyone trying to predict how things will look in 5, 10, 20 years really must have a crystal ball. It's interesting to hear that things aren't always as set in stone as the forums may have you believe.
I think a lot of the arguments over time to command are only likely to matter if it's really, really important to you to have that LHS asap, 4 stripes and a fancier hat (ok, that's perhaps being a little trite, of course the extra responsibility and status is appealing). Ultimately, if you're lucky enough to get taken onto the FPP, especially if you're coming from another career, it's still a life-changing move. You still get to fly outstanding aircraft for the remainder of your career, to a huge range of destinations, meeting and working with interesting and (hopefully mostly) motivated individuals, with a very comfortable salary and lifestyle with pretty much unparalleled benefits compared to 99% of the jobs out there, whether aviation related or otherwise.
The argument about joining late and not making it to the top of the 34 point pay scale just doesn't strike me as a particularly big issue. I won't make it to ppt34 unless they raise retirement age to at least 69! I also couldn't care less. I'm coming from a career where it tops out a mile below what BA can offer, and my bosses and professors all live very comfortable lifestyles as it is.
If time to command and reaching the top of the company payscale are at the top of the list of priorities, there are other avenues out there. Everyone has their own vision of where they'd like to be. Good luck to them!