it's too early for information on events in 2011 in Tuscany. As a matter of fact most events, such as local fairs and festival, aren't advertised much in advance at all. Most of them will be advertised 2-3 weeks before.
Anyway, I checked past events to see if in April-May 2010 there were big annual events but I didn't find anything related to wine.
I suggest you check often our updatedevents calendar in Tuscany and our blog about Tuscany because we usually post information and suggestions about Tuscany events. I also recommend you check back and post your question next year, sometime in March-April-May since we might be able to tell you more then