In the end, I don't think there will be too many people who care enough about a sealed battery or internal memory to sway their decision. If the phone is one of the superior products on the market, people will buy it.
The removable battery pack is a bit overrated, imo, for the simple fact that by and large, the battery that comes with the phone is most likely going to last you 1 year or 2 until you decide to upgrade to another model. Smartphones are basically "disposable" these days and the amount of people who keep them beyond the life of the contract with their carrier are significantly decreasing. So most people will probably never have to actually replace the battery. The only people I can see being affected are really heavy users who need to swap batteries halfway through the day.
As for the expandable memory, the benefit to this is mostly just in the up front cost of the phone (or your monthly payment if you're on a plan like AT&T Next), and it's really not that dramatic of a price increase. Using the current pricing for AT&T Next, an S6 with 32gb of storage will cost you $22.84 per month for 24 months. The 128gb S6 will cost $29.50/month. Over 2 years, that comes out to an additional $159.36 for the 128gb version. Comparatively, you'd probably spend around $100 for a 128gb card, so the cost difference is somewhere around $60 spread out over 24 months....or $2.50/month. If $2.50/month is putting you in a financial bind, you may want to reevaluate your finances instead of worrying about getting the latest and greatest phone.
Again, the only people I could see really being impacted by the lack of expandable memory are more "power users" who carry multiple micro sd cards on them throughout the day and swap them in and out based on their content. I think this applies to a relatively small portion of users, too, though.
Do I like having a removable battery and expandable memory? Sure. Would it actually sway my decision? Most likely, no.