Here's my 2 pennies......
1) Templates. This would include the ability to have each board act different from each other. So one board coulld be a straight flat view...another be a threaded view and yet another would be a new view which would be strictly linear chronological. The reason linear chronological is good is for conversation stlye boards where you wouldn't want threads......Each post and reply is put to the top of the listing in a chronological order. It would be good to have the ability to force these views so they either could or could not be changed by the end user in the Control Panel on a per-board basis. I am affraid I may loose my visitors without the incorporation of a linear chronological view (For that one board they are using)....it's what my visitors are used to and they're getting flustered with the current setup.
2) Site integration. The only thing I can think of in this regard is so I can put a line of text on the front page, or other pages, that would say how many people are on the site or that particular web page. Also to be able to have the flashing envelop in pages to tell someone they have a private message waiting for them in the forum.
3) Existing hacks. As I've said many times here....I would like to see the inclusion of the existing hacks successfully incorporated into w3t. Like that Bozo hack that I've yet to get to work for me with ver 5.4.2 []/testimages/icons/frown.gif[/]