"Is <xyz> going to be a daily deal?"
Valve selects a range of stuff to be the daily deal. They typically include a handful of larger, mega-publisher games, a handful of quirky PC mid-tier publisher games, and a handful of independent games. Now that early access is a thing, they're going to include the scattered early access game. In general the games featured as daily deals and flash deals are willing to discount at least 50%. In general Valve is picking games that people would be interested in, so high popularity games or games they think have a certain level of breakout potential. Most of the games they choose review well, although not all. Games that are part of a daily deal typically show up as daily deals in subsequent sales (and publishers who participate typically participate again later). In general I would guess that if Amazon or GMG or whatever have significantly better deals than the Steam sale discount, there's at least some possibility of it being a subsequent daily deal.
There are exactly two ways you can be sure that something won't be a daily deal:
- When the dev explicitly says there won't be a daily deal
- When a game is obviously abandoned, not on sale at all, and either has a defunct publisher or a publisher who has never shown any interest in Steam at all at any point in time. (IE The Doctor Who Adventures, currently on 0% discount, aren't magically going to be a daily deal)
Now there is no reason to ask whether or not something is going to be a daily deal.