The IEEE Standards Board has formally ratified the 802.11n standard (802.11n-2009, to be extraordinarily specific). It took seven years and involved 400 members from 20 countries. Somebody deserves a vacation.
Successor standards committee's are already underway, of course, but it's likely years before we see products based on 802.11ac (6 GHz and below) and 802.11ad (60 GHz), both of which aim for speeds of 1 Gbps and faster.
Somebody go put masking tape over the word "draft" on all those Wi-Fi boxes.
As far as any firmware revisions based on tweaky late changes to the spec, it's unlikely. From what I can tell from colleagues and the Wi-Fi Alliance, it's much more likely that newer devices will add features than current devices will see (or require) firmware changes.
On 7-August-2009, I wrote up the four major additional features coming to the Wi-Fi certification process, some of which were dependent on the late-stage draft changes in 802.11n. See "The Fine Points of Optional Wi-Fi 802.11n Certification."
The four new certification elements mostly, but not entirely, related to improving raw speed or net throughput.