Hardy was only on the field for 6-7 plays in Week 2, and I think 2 plays in Week 1 (0 targets). He is being brought along slowly, because he is still pretty raw & missed a lot of preseason with a hammy injury. He is a great red zone threat & will always be in there at the GL in passing situations. Aside from GL work, he's getting a little more action with each week, and his TD probably accelerated that a little for Week 3.
Reed is slow, but one of the better 3rd down possession WRs in the league. He is best suited for the slot, so Hardy will overtake him at some point this year. I doubt it's before mid-season though. He doesn't play the same position as Parrish, they are not competing for time. Parrish plays strictly in the slot.
He won't get more than 2-3 targets/game for another few weeks at best. I wouldn't even consider starting him until week 8-10. He's a good bet for 6 TDs this year, but his biggest contribution for the Bills will be drawing coverage away from Evans.