First, I think there needs to be more clarification. 0-2, 1-2 is quite different than 3-2. You can further drill down by "depends on the hitter" and "depends on the pitcher". That said, I'll assume you mean behind in the count and "most hitters/pitchers".
Generally, I'm not OK with a total sell out for any pitch with two strikes. I belong mostly in the traditional camp that calls for some adjustment with a behind-in-the-count two-strike approach, usually a widening of the zone and more of a get-the-bat-on-the-ball mentality. I do have some variance, though. To your point, I recognize that most P's will try to work down and away (and occasionally up) when ahead. I like a hitter to get closer to the plate and look for that pitch. This does a couple things... 1. dares the P to come inside, risking hitting the batter. 2. gives the batter confidence that he is definitely able to cover the pitch on the outside black as well as knowing that something that looks outside is definitely outside. 3. somewhat negates the advantage the pitcher has gained. Yes, this leaves hitter a bit more susceptible to inside pitches but I don't want the total sellout. Fight that one off or take the HBP.
There are some hitter types that I am OK with not changing their approach when behind in the count. But this is usually the type that gets on top of the plate and bashes at everything to begin with. Either that or hitters that have very good zone awareness, read pitches well and have a sense for pitch sequence.