The game is not going to be made in a old-school Sierra adventure style, but rather in a 2D tile-based format it seems. The reason for this is simply budget constraints. QFG 4 was made with about a $1m budget and QFG 5 was made with a roughly 4-5m budget.
They've already stated on their website they won't upgrade to a Sierra-style interface with a stretch goal as it'd be a complete redesign of the game and not what many people expected when they backed it. Of course, this doesn't mean future games in the series (yes, it's planned as a series with different characters for each game) might not get a upgraded interface.
While the game is not quite what I would wish, I'd prefer an old-school QFG style one even if it looked like QFG2 or 3, I'm happily backing this project.
For those not familiar with the people behind it, or just want to see an interview with one half of the husband/wife team that created QFG here's a link to an interview done a few days ago. Too long to post here, sorry.