I don't think anyone expects them to be any where near the front of the grid in their first season: it takes time, experience and money to get to the front end of a Formula One grid, it doesn't just happen. It shouldn't, however, be completely ruled out that they could be in the midfield. If they have the money to produce a good car, combined with a good pair of drivers, they could see themselves in a good position but shouldn't get their hopes too high.
Let's be honest, the more money a team spends on their car in Formula One the faster it will be. It has been that way for years and years, and will continue to be that way for many more. Haas don't have the budget of Mercedes or Ferrari but they are going to run on a Ferrari engine which has had a lot of money thrown at it and, as a result, has a fair bit of grunt to it!
With not much experience within the team and possibly a lack of investment may see Haas towards the back of the grid. However, with probably a higher budget than Manor, gaining in experience, and hopefully a profit, we could see them climb up the grid slightly by the back end of the season.
2017 could bring bad news or good news to the teams on the grid; with major rule changes we could see some teams leap frogging others and some teams losing out on pace compared to previous years. This, as with any other team, could bring fortune or devastation for Haas F1 Team. After just one season of being in the sport would you want it to change dramatically?
If they do a good job, they could jump a team or two themselves but it may take years for Haas to be considered as a midfield team. All the workers at the factory can do is work flat out (as always in F1) and develop as fast as possible during 2016 as they have to play 'catch up'.