The Mac Pro will soon be discontinued in Europe (nanny-state regulatory requirements). Apple will no longer accept orders for the Mac Pro in the EU after Feb 18th.
The rumor on various sites is that a new Mac Pro will appear in the “spring”. These rumors cite a French retailer that claims having been informed by Apple as such.
Keep in mind that 'spring' runs through June 20, the 21st being the summer solstice, and that an announcement and a shipping product can be separated by a month or more, as the latest iMac demonstrates.
The timing seems reasonable, but it’s unclear whether such a release date could incorporate both Xeon CPUs and USB3 onto the motherboard. However, Ars Technica discusses a new server class chip around the June timeframe and such a confluence makes sense to me.
Another concern is whether we could expect a conventional Mac Pro form factor or possibly something less capable but imbued with more Apple “coolness”, an unpleasant idea which cannot be ruled out.
Apple ought to make a formal statement on the matter, particularly for European customers. While highly unusual, my prediction is that there is a 50/50 chance that Apple will issue at least a vague guidance once the Mac Pro goes off-sale in Europe.