I like the looks of this track, especially the kerbs seem closer to real footage compared to the current version. Anyway, as Johannes pointed out, we have a lack of personnel at moment in track testing, meaning it would be a very risky move for FSR to use an untested track, as potential bugs could appear later on which could not be fixed then.
Secondly, switching the track a week after release does not work in practise. It might be worth refreshing that FSR is run by the ISR Club, which in turn is owned by the World Championship team owners. Not to speak against anyone in particular, but team owners have their own competitive interests, to which changing the track a week later does not fit (which is also a shame in a way). The WC is quite an elite business, meaning teams have to start testing well before the second week if they want to have any chance of running for good point positions, at least that's the case in the beginning season when the mod is "new".