The 764 does indeed have raked wingtips, which are more efficient than blended winglets that 763s have.
The 777 wing comes in two sizes,
200' wingspan which is for the 772A, 772ER and 773 non-ER - these do not have winglets or raked wingtips
213' wingspan is for the 772LR, 772F and 77W and have raked wingtips.
Raked wingtips is the reason that it is claimed that the 772LR is actually burns less fuel than the lighter 772ER on ULH routes.
787s have raked wingtips.
I agree the 772ER getting winglets may require too much structural work to be economical to install or sCO would have probably jumped on it pre merger.