I haven't travelled the route, but as I understand it the electrified route between Buchloe and Lindau will be that via Memmingen, not the present main line via Kempten.
Memmingen-Hergatz (62km) and Memmingen-Buchloe (42km) are single track, whereas the route via Kempten is double track (as per the Schweers atlas), though maybe some upgrades on the Memmingen route are planned (I can see a major bridge near Hergatz has been replaced).
Today's through Zürich-München trains travel via Kempten.
Presumably the Kempten route will become a local line after the change.
en.wikipedia.org
Presumably DB's ICE-T sets could also work the new route.
They started life on Stuttgart-Zürich services.