If yes, why not? :-) Seriously, it's about time: we're deeply in module development now but there's no reason not to start working on your theme already: you know everything about theme development! (OK, maybe not everything but every essential information to create your theme.)
Remember: the earlier you start making use of our offer to review your code (see the FAQ) the more reviews we can give you. If you have questions, go on and ask them in the Orchard discussion board (and if you have read the FAQ you also know how to make sure that if nobody else, we'll help you there).
Also, Dojo Course news are announced on Lombiq's Twitter feed too, so follow us to keep up to date.