Then Morrisons may swallow up Asda which they did with Safeway as it may be perceived as slightly more upmarket than Asda also it is older having been established at the turn of the century (1890s-1900s) which Asda began in the 1960s if I'm right?
I'm not sure that any of the current Big Four (Asda, Morrison's, Sainsbury's and Tesco) could really be considered as more up-market than the others. If you want "up-market" you'd go to Markie's or Waitrose and even then you'll find that the stuff you buy is produced in the same factories as the stuff that their competitors' products are made.
Supermarkets essentially have three tiers: the "Extra special/specially selected" range, the "normal" own-brand range and then the budget "savers/essentials" ranges, many of which have been re-branded with silly artificial names - presumably to compete with the likes of Aldi and Lidl.
They've all had to deal with the so-called "discount" stores over the years, and I'm not just referring to the resurgence of Aldi and Lidl; Kwik-save and Shoprite competed at the lower end of the market for years before the Germans came along. There was a bit of a "bean war" for a time, when all retailers were trying to out-do their competitors by selling baked beans at silly prices; the budget ranges had baked beans at less than 10p a tin for quite a while.
As an aside, I used to have a regular customer who would demand help with packing her shopping, but it had to go in the Marks and Spencer bags that she provided; presumably she didn't want the neighbours to see that she shopped at Safeway...