merits of 802.11a in an 802.11n/ac world?

Salut,

If one 'upgraded' to the 802.11a standard of yesteryear today (in order to
avoid 2.4ghz congestion), how would it fare in the coming years when 5Ghz
n and ac become more prolific?

Is there anything about the old a standard or the newer n/ac standards
that would mean that interference between the 2 (or 3) would be less
considerable than that caused by the overlap of today's 2.4Ghz routers?

I'm thinking along the lines of beam forming, or channel width, or perhaps
error correction.

Any ideas??