Guys, what do you think, will the new release (guest, visitors, etc) compatible with the current one? Is it worth to start a new fort, or better to wait?
To add to what was said above...
Toady has been working in a pattern for the past 9 years.
Step 1: "I'm going to add a new feature this time. May take a couple weeks."
Step 2: <couple weeks later> "Oh, hey, there's progress, but there were some problems that will take some extra time to work on."
Step 3: <couple months later> "Hey, guys, I stopped doing what I said I was doing because I'm working on some totally random side project!"
Step 4: <a year later> "Hey, anyone still checking these things? Oh, well, I'm releasing a new version, now. It doesn't have anything I said I was working on, but it has all that other random stuff, instead, so enjoy!"
(This is the point when everything is horribly buggy and broken again as it is a new version.)
Step 5: <2 hours after new release> "Oh, wow, it turns out my first version has a crash bug as soon as you perform any designations or chop wood, whoops! Hotfix tonight!"
Step 6: <1 day after newest version> "OK, so I'm going to fix some more of the obvious bugs then go to sleep."
Step 7: <8 hours after newest version> "Oh, wow, my bugfix caused more crash-on-launch bugs, whoops! New hotfix!"
Repeat steps 6 and 7 until the most blatant of bugs are fixed.
Step 8: Maybe add some features in a two-week timespan.
Step 9: Back to bugfixes once a week or so that increasingly grow more major.
Step 10: Decides to go back to adding a feature, at which point, go back to Step 1.
For what it's worth, this tavern and caravan arc stuff Toady's declared he's working on? That's what he declared he was working on in 2010. That's certainly not to say that worldgen cities or vampires or minecarts weren't great additions to the game (minecarts and wheelbarrows in particular solved one of the most critical problems in the game) but just that you shouldn't trust Toady's rough speculative guesses about when he'll be done with anything.
So yeah, don't hold your breath. This is the good time to start a new long-term fort, when all the bugs are known and have the best workarounds available, and you aren't likely to have giant save-breaking version shifts. In fact, even if he were coming out with a new version tommorow, I'd suggest you keep playing the version we have now, because the new version is going to be a constant flurry of version updates (many of which save-break) that doesn't settle down for a couple months.