Transceivers for various 10-gigabit PON technologies (10GEPON, 10GPON, XGPON) have begun to hit the market, but OLT modules have so far only been available in the XFP form factor. Does the smaller power budget available in SFP+ prevent 10 gigabit PON OLT modules from making their way eventually to the smaller form factor?
SFP+ power budgets are typically in the 1 - 1.5W range as a function of the density deployed (i.e. 48p in a 1U form factor) and the ability to dissipate heat in such a small package. 10G PON SFP's exist but likely are pulling power outside what's usually appropriate for SFP+'s typical use case.
At the moment the maximum SFP+ power I've heard of in common use is a 40km capable 10GB-ZR, and even that isn't universally supported on all platforms. I would imagine that further DSP development will drive power requirements down - which may make it both cheaper and more practical for the smaller form factors.