Assad's crimes and destruction have made him such a hot potato he may have nowhere to go. Venezuela is impractical while Putin just made it clear that Assad can't look to Russia either.
Similar political and economic reasons will likely lead China and Iran to say "no" as well. When it comes to making disasterous long-range political decisons, Khamenei is as much as disaster as Assad, so you never know.
In the end, invited or not, Assad may have no choice but to head for Tehran. if he can catch a last-minute plane and load it with cash and gold while a usable airport remains open. But what will the mullahs do as his plan enters Iranian air space. Now there's an intteresting situation.
I look at that in a subpost in today's Syria Live roundup at Enduring America. I'd have posted the item here intact, if cut and paste were available under this new layout which is pretty enough otherwise. You can't even copy and paste a link.
I hope that problem can be worked out soon. Thanks.