Tesla has long pooh-poohed the notion of pairing ultracapacitors with li-ion cells, and IMHO with very good reason. Maxwell appears to have been focused these past several years on adapting their electrode tech for li-ion cells (see the above link), and it looks quite useful.
Yup, year back I heard the same talk. But I think they are gonna do more R&D to research and integrate.
Also what Tesla says in public might not be what it is really doing in reality.
My understanding is Ultracapacitors can charge/store energy faster, but they cannot hold the energy as efficiently as Li cells. So I think there are good efficiencies to be derived from using them both.(charging time&efficiency) ..
Maxwell Technologies Transportation Solutions: Automobile
~ cheers