Any issue with upgrading lang/tcl to 8.5.12 ?

[John Marino <netbsd%marino.st@localhost>]

I've been requested to update a package that requires a minimum version 
of TCL as 8.5.0.  This is not entirely unreasonable given that 8.5.0 was 
released in December, 2007, nearly 6 years ago.

pkgsrc is still on the 8.4 series of lang/tcl.
Is there any reason we can't or shouldn't upgrade?
I'm asking before I attempt it in case there's some background info I 
don't know.

John