This is something that is being worked on currently. Don't expect to see official statement before monday - noone, except me, works on weekends
Also, it wasn't all about merging just forums - but merging four 1000+ user databases, that all had unique data structures. Because I don't know much about the process, I can't comment on wether it was a good idea to close existing sites until process was completed. But I'm quite sure there were good reasons to do so.
Also, TCL will not be replaced by LUA. TCL will propably come as module (which also will apply eventually to PHP).. writing a module takes somewhat more time, because one needs to map all the functions io provides to variables.. which is why I've favored statically linked tcl & php libraries.