Are Cat6a keystone jacks suitable for Cat7 Ethernet cabling?
No, you won't get the 25Gb Cat 7 bandwidth with Cat 6a termination. For 25Gb speeds you need to terminate with GG45 (GigaGate45), ARJ45, or TERA, but not RJ45. 

I think you should use 6a termination so you'll get 10Gb, but if 10+Gb becomes available in the future you can replace the terminations if needed. 

GG45 is a product sold by Nexans that is backwards compatible with RJ45 at 10Gb speeds. ARJ45 is the ISO standard non-brand name that is similar to GG45 but might be easier to find. TERA is a product sold by Siemon, but isn't backwards compatible with RJ45, so it's not as common.