I know it's only anecdotal but there's a brand new Bunnings in Forbes NSW (real close to Parkes) and it's beeeauutiful. I've only been out this way for a few years but the first thing I noticed when I moved here is how many unrenovated properties there are. Now we can all make our houses nice.
I'm sure they go for unrenovated areas where the household income is increasing from very low to not so low to not too bad now, as mentioned above.
As for IKEA - my impression is that they plant themselves in areas where there are young people renting and buying and where there's easy access and in an area that is/was slightly industrial so they can use up lots of space. They want to be as close to as many young people suburbs as possible but the site itself may be a way off gentrification.
As already said, there are less IKEAs so more important to get as much access from as many different routes as possible.
But Bunnings = impending gentrification, yes. imo
There are also certain govt programs and courses run at TAFE that I look out for i.e. a lower socio-economic region but lots of young 'uns.
Believe me or not but the large enough site with the right 'bulky goods zoning', established population around the site and large enough catchment area (no completion or existing Bunnings store close by) are the most important criterias when Bunnings chooses sites to their new stores. It is hard enough to find sites that fill those criterias, so immediate suburb's gentrification potential does not have impact on decision making. It's plus, but not criteria. Customers travels quite far to get to the closest Bunnings, so immediate neighbourhood does not matter as much as for Coles or Woolies when they make decision where new supermarkets will be opened.