Personally, I don't see it that way, but I can understand that others' experiences may differ.
I say that because I was in a group for several years where I played in RPG systems that were not to my liking- esp. a buttload of GURPS (the default system for most of the gamers in the group) and 5 or 6 different mecha-themed games- between campaigns of D&D and HERO. I did it for group unity (it was a very cool group), and because I knew that at some point, one of my preferred games would be up in the rotation again. Even if I had to run it.
And sometimes, it took a while. But we rotated screen monkey duties throughout the group...with mixed results. Still, that meant the pain was both spread out and shared.
It's not as if (returning to the present situation) the 4Ed DM intends o run this game forever. He, too, intends to take a break at some point. When he does, IF the 3.X guy is recharged, that will be the game. If not...
Well, it's not as if anyone else is making noises about running a game right now.
For the record, I've run a RIFTS, 3Ed and M&M game in this group over the past 13 years...all short-lived. There have also been 2 2Ed and 2 other 3Ed games run in that time period. Besides this 4Ed game, only my M&M game had less than full participation.
It's also not like I'm pro-4Ed, either. While i consider some aspects of 4Ed to be superior (like the Warlock), I GREATLY prefer 3.5. But I also recognize that, even though it's not my fave, I can and AM having fun roleplaying a PC in a well-run game. (Especially knowing that there is a light at the end of the tunnel.)