It looks like there are already 535 with updated hardware released. At the wpcentral forums the user "zed 3250" mentioned it:
i believe it's really a hardware problem:
i bought mine from amazon france around 3 weeks ago and it does have the touch problem, but i've seen people from french forums who recently (3~4 days ago) bought the phone reporting no issues whatsoever, even without the update (it's not out yet in france).
I've even asked one of them about his hardware version and he said it was 0.5.0.1 (which is weird because mine was 3.0.0).
I really hope microsoft will make an official statement about this.
OP is asking how to check the Hardware Revision number without unpacking the devices in the box. There are 2 versions of the Lumia 535. They are some people saying that the older hardware version 188.8.131.52 has this sensitivity touch issue while the 0.5.0.1 doesn't have.
The OP wants to ensure he gets 0.5.0.1 version so that there is no issue with the Touch Issue. Does the box has the information with the Hardware Revision Number? I too want to buy but I need to confirm this first.