We've had a few promotional-grants recently (thanks!), and the pattern is generally that when there's more interest than grants the highest rep users get the goods.
This absolutely makes sense, rewarding those people that are contributing to the site. However, it does bias the grants towards those of us that have been participating for the longest time.
My suggestion is that some of the grants (assuming there are more; please!) get broken up into two groups: highest-rep (like in the past) and highest-rep-recently (e.g. highest this month or highest this quarter).
This still rewards contributing to the site, but opens it up to someone that's new here. You'd still have to do a reasonable amount of work to get to the top of the monthly (or especially quarterly) rankings, and those users with a big backlog of answers do have an advantage, since old questions/answers do continually pull in a trickle of rep.
(Perhaps there could even be the odd grant rewarding something else? e.g. number of edits, or number of accepted answers regardless of rep? (e.g. story-identification doesn't pull in much rep)).