Short term news is probably moot, as there are as many limitations as there are benefits to how id Software delivers source; long term were Coroner say to Open Source a game like True Combat: Elite, it could mean a lot.
The GPL License
Currently all TC:E and CQB work can bey copyright, closed source and prospectively repurposed in some commercial work on some other engine, like our Moose Engine
which will ship with a modified MIT License
for mod Developers. On ET Source, TC:E or CQB would eventually have to be FOSS games...
Assets Not Included
id Tech engine source is typically engine only source, which eliminates all art assets and often a lot of game-function top-code that TC:E, CQB may rely on. A cursory look at the ET source shows it includes a surprising number of features, but there's a lot that isn't there that will be tedious and time consuming even for a capable and ambitious team with a lot of free time to code/create.
While W:ET is functionally at EOL, it and its Mods still benefit from: Master Servers and Punk Buster, and though Punk Buster has it's license EOL, it still protects in it's final resting state against a bevy of annoying cheats and exploits that would run amok on an FOSS game.
Coroner gets access to source that may help him address more design and functional issues -- which may add more time then planned, and slow CQB development to some extent, but help deliver a better game more along the lines of his design intentions and goals.
Obviously True Combat, and True Combat: Elite could never have happened were it not for id Software's generous mod support, and source policy; with that in mind it wouldn't seem unreasonable at some future date that TC, TC:E or even CQB would be released as an FOSS game(s), returning benefit in kind, establishing long term good will and recognition for all the design precedents TC set for gaming rather then ending up at the bottom of the heap of mod oblivion and forgotten mods.
Of course Coroner is still actively developing id Tech engine mods, so it's unlikely the news will have any immediately perceivable benefit in 'Gamer Land'...