That was probably the last PPC they did and was probably ready when Apple made the announcement. It just wasn't worth for IBM to invest in workstation-class PowerPC chips with laptop power envelopes. The only other use for PowerPCs, from their PoV, was their own workstations and those could use the higher end POWER chips.
IBM continued making PowerPC G3 derivatives for a while for Nintendo. Nintendo ended Wii U production in January 2017, which would I guess would mark the end of IBM's production of PowerPC as well.
The Wii U for all its flaws is probably the most "practical" Power-based machine you can get nowadays, given relative power, availability, size and price. A 1.2GHz triple core PowerPC G3 would probably still eek out Raspberry Pi 3 like performance. Shame the Linux port to it never really got off the ground (also partially due to IBM's hackjob of an SMP implementation for the G3).
