Currently Airing Anime

Apparently NGNL's LN sales shot through the roof, but the BD sales were far more modest.

I don't know if i'd call it shot through the roof though unless you're only comparing it to pre-anime sales of itself in which case it definitely did shoot through the roof, however if compared to the big LNs its sales were definitely an improvement but nowhere near the 'roof'. Although considering that NGNL is relatively new it might not be fair to compare it to the big LNs.

I mean the anime did a great job advertising though, it definitely improved the sales of the LNs by a lot compared to the sales of the LN before the anime.
But who knows, season 3 of DxD just got announced and it definitely isn't near the big LNs either so another season of NGNL might not be too unrealistic. One can hope.

I'd probably enjoy another season of NGNL, could be fun.