I do not see why templates will not have acceptance. If the default templates recreate wwwthreads as you ship it now (in other words, templates will reflect the actual wwwthreads look) there should be nothing to fear. If the customer want further customization, then the templates are there, ready to be changed. The other solution to not having templates is to edit every script, one by one, manually and loosing the changes on the next upgrade, which one is better? To be honest, the actual look of wwwthreads is not that great and I have seen people who purchased the product made little or no changes to it, which I consider it lame (yeah, I can see the flames already).
The lacking of templates is what is holding me back from buying wwwthreads. And I think that if you are going to implement templates, you should do it all (all scripts) or nothing. There is nothing more annoying than a work half done.
Cheers!