RichardInSF-san,

Yes, you will be able to use Suica on riding keio bus.
And you can get discounts (as long as keio bus press release mentions so.)

On March 18th, Keio bus will start this service on bus lines which departs from following railway stations.
Keio-Line
Shinjuku,Hatsudai,Sasaduka,Hachiman-yama,Musashino-dai,Tama-reien,Higashi-Fuchu,Fuchu

Keio-Inokashira-Line
Shibuya,Eifukucho,Kugayama

JR-East-Line
Nakano,Koenji,Asagaya,Mitaka,Musashisakai,Higashi-koganei,Musashi-sakai,Kokubunji,Nishi-kokubunji,Kunitachi

Also served in:
Keio line Chofueki-Kitaguchi to Musashi-koganei(#91,#92)
Keio line Bubai-gawara to Kenko-Center(#52)

Not served in following bus line:
Local community bus line
Circle line departs from Shinjuku
Kunitachi to Seiseki-Sakuragaoka(#18)

(Original Japanese press release is http://www1.keio-bus.com/pdf/ic_card_service.pdf )