A lot of folks have been making noises lately about how they're getting off of Second Life and going to other grids. InWorldz seems especially popular right at the moment, but others have been mentioned. The Phoenix Viewer team has been approached about becoming the official viewer for one grid.
I'll be staying on SL, myself, until they turn the lights out. Why? It's where my friends are.
A lot of people see SL as just a place to play games, or to harass people, or MAKE LINDEN$ FA$T!, or have random pixel sex with anyone they can entice onto a poseball. Naturally, they think that the rest of SL is in it for the same kind of reason. Those folks can switch grids pretty much as they wish.
To me, SL is a much different place. It's where I can meet my friends and spend time with them in a world of our own making. The key word in that sentence is "friends". I have RL friends that I knew before I'd ever heard of SL who are on there with me. If my friends aren't on InWorldz, then the place isn't interesting to me.
Yes, I enjoy sex on SL. I sell stuff (not a lot of it, not even enough to pay my rent, but some). I play a game, as a Princess in the Tiny Empires Kingdom of Home. That last is revealing, in itself: TE is an explicitly social game. It's not about gaining rank or accumulating gold and acres. It's something to do while you spend time with friends.
My friends aren't on InWorldz, although one of them is considering setting up a presence there. I set up an InWorldz account the other day. I got logged in, poked at it for a bit, found that Phoenix runs fine over there, and lost interest. Why? Because none of my friends were there to talk to.
There's a secondary problem, but one that is no less real. I couldn't get a nice tigress avatar on InWorldz. My avatar is the version 3 tigress from AnthroXtacy (and I highly recommend them; they do fantastic work!). I looked around InWorldz and couldn't find anything at all in the way of a furry avatar. Nothing. Not a blessed thing. There's supposedly a feline avatar in the freebies store at the island where new folks to InWorldz land, but I wasn't able to wade through the severe lag there to actually locate it, let alone lay a paw on it.
This points out something more fundamental. SL is full of user-generated content. Very full. It's easy to obtain and cheap on the grand scale of things: my nice avatar cost me all of US$3. People on SL don't truly appreciate just how easy it is to find and buy stuff, even with search and the Marketplace as broken as they are. I didn't until I went to InWorldz. There, the selection is much more limited, and many categories are missing altogether.
Why isn't there more content? Because InWorldz is a separate grid from SL, you can't just have your SL inventory appear there. It's worse for a content creator. Using a viewer such as Phoenix, you can export your own creations to disk and then re-import them. The problem is that this is not and cannot be a complete copy. You have to export each individual object. You then have to import the object to the new grid, upload every texture (they're not saved on export), upload every script (because the client cannot export those), then manually marry them all. Repeat for each object. For an avatar maker, there are lots of those per avatar. Multiply that by 200 avatars, in the case of AX, and you have an immense amount of work.
On top of that, there's a technical issue. While the Second Life viewer code is open source, the server code, and the stuff that backs it up such as the asset infrastructure, is most definitely not. A group of folks has created an open source workalike called OpenSim. The problem is that it's only a workalike, and in particular contains some incompatibilities around the scripting engine. Those incompatibilities are why I rent a SL homestead sim to do script tuning instead of just using OpenSim.
This all means that, once again, we have a chicken-and-egg problem, just as LL does with mesh. It's a lot of work for content creators to establish a presence on InWorldz, or any other grid. They're not going to attempt that unless there's money in it for them. Where are the users? Waiting for their friends, and their content, to make the switch. Without users, where's the money?
I do believe there's a future in alternate grids such as InWorldz, if for no other reason than LL seems intent on shooting itself repeatedly in the foot until it dies of gangrene. I'm not a good enough fortune teller to guess as to how much future there is there. One day, if SL becomes untenable for some reason, I might move to another grid. That day is not today, nor is it any day in my foreseeable future.