I would say "No" to that question in both parts.
SRO:
There are generally 3 to 4 games ongoing at any given time. The last several weeks have been uncharacteristically low for SRO, but my guess is that as soon as the games get running smoothly again, the players will return to posting. We have somewhere between 5 and 20 regular players, depending on the week you check in. In addition to those, there are generally 3-5 regular GMs, who are likely to enroll in an occasional game as well, totalling somewhere in the 10-25 total players range.
These players change as their real-life requirements shift allowing for more, or less, time to post. This is a generally on-going cycle, and will likely continue for PBP games (not just SR) ad infinitum. The players who are comfortable with this often become GMs as well, as their posting rate does not fall off after a shorter period of time.
SR:
I have a loyal Table-Top group who play Shadowrun one night every week. Of the 6 of us, 3 are married, and 2 of those three have children. Their husbands, by and large, are not interested in Shadowrun, but appreciate the "give a little, get a little" opportunity of supporting their wives' play-nights, and getting a night of their own free to meet up with their buddies.
I am, on occasion, invited to GM for larger games, "Meetup" nights, and even the occasional Test Night or Tournament. Relative to the total number of RPG players who are willing to play Shadowrun in general, I don't believe that I have noticed a significant drop in numbers over the past several years. While it is somewhat difficult to build a group, as most SR players now have a dedicated group, it may be a somewhat simpler matter to join an existing group.
My group and I occasionally indulge in some of the other RPG worlds, just to keep our horizons broad. We play, from time to time, LARP, VTM, D&D, Earthdawn, among others. We also, on occasion, post a Meetup for the express purpose of attracting new players to our group. Strangely, we often have a large handful of players show up for the night, but it is an extremely rare occasion that we gain any more than 1 player out of 10 or so for the long haul.
In short: No, SR isn't dead. It has become somewhat more regimented though. The players have their groups and are generally content to stick with them. Even on SRO that seems to be a somewhat repeating theme. The same several players are the key-note players keeping a game rolling. Often if even one of those players is absent for RL issues, the entire game comes apart. Sometimes to be resurrected once that player returns.