I'm fairly certain our site numbers are actually improving. I've been keeping a loose list of members online at certain times of the day (as in, when I check

) and we're consistently getting more and more members online. Been logging on more frequently to find 70-80+ members+guests (not spiders/bots.)
I'm really speculating here, but based on our "how old are you thread," we had almost an equal part of members that are baby-boomer and traditionalist aged; which are two age demographics not exactly known for embracing change, especially with technology.
We completely changed the site with the upgrade; lost out on thousands of likes, reputations, and a lot of member photos got bunked, which I think turned off a lot of those people. Hell, I lost almost 20,000 reputation points on the old site AND all of my pictures are gone because of the way I uploaded them! Is what it is; at the end of the day you can lead the horse to water, but you can't make 'em drink (stole that from Blue!)
We also took a hit on our google ranking after the upgrade (which I believe is restored; first site that comes up on a search!) That probably didn't do a ton of favors when people were searching for us the past few months.
That's just my opinion/speculation on what happened.
But like I said; based on what I've personally seen, we are improving in site stats and numbers, it's just not as fast as I'm sure all of us would like to see. Used to log on with HUNDREDS of members on-site (and lots of stuff to do always!) Well, we'll get there again.
This is a community, communities grow as we grow with each other!