Unless it's been the subject of a clever badge-swap, this is a V10 model (as are all R8s at the moment), although rumors, leaked product roadmaps, and common sense point to a downsized engine offering in the near future. We think it'll be a V6, based on the fact that the R8 technical lead Roland Schala stated that a "V6 is a perfect engine for this car."
Don't expect any drastic mechanical differences from the coupe, itself a close cousin of the Lamborghini Huracán. We thought the coupe was "murderously fast and sexy," while still being a tasteful, total driver's package; the Spyder should bring all that and some open air to the table. We should see the R8 Spyder's official reveal in a few months.