Hi,
Yeah they reworked their API's entirely. However you do get a $200 credit each month.
So if you wanted static maps, or geocoding or whatever then you would use those API's.
I'm unsure if ggmap and others may have compensated for it.
I've resulted in working with OSM and pretty decent.
And R has the leaflet package, which is simply amazing.
Just depends on what you want to do really.
Kind Regards
Vickus