The Slate is already like 2 years old if i remember correctly, so no.
From GL usually routers are getting around 3 years support, but their life is extended using Vanilla OpenWRT.
What ccchan is talking about is that Vanilla OpenWRT has not had NAND support, while the GL firmware has, so compiling your own OpenWRT firmware, without using the GL Imagebuilder, would result in a NOR firmware only.
All the modifications are already done, its just the OpenWRT team that maybe has decided not to include it. They temporarily dropped support for the AR750s already, but users have been pushing fixes for it to be included again. You can read about it here, and the progress:
All the sources are here:
And here is the AR750s NAND:
Also when i said 3 years, its not a hard limit. The AR750s is one of the most popular routers that GL sells. As with all open source projects, once support is over, fixes will still trickle in from the community and if you are a good customer and ask nicely