I think by superbrands you mean what I would call MasterBrands - these are large brands that have can have a number of sub-brands beneath them. For example Zara has Zara clothes, Zara kids, Zara homeware etc.
Counter to your questions most businesses see these brands as a positive thing. It allows the benefits of the brands (trust, dependability etc) to be transferred into new areas.
Whilst it is true that it is more difficult for a Masterbrand to move upmarket than downmarket there are exceptions that break the rule.
For an example of a downmarket brand trying to move upmarket look at H&M. It's collaboration with designers such as Versace can create a Halo on the brand, that whilst not shifting it up to the designer level, does make it rise above its peers. Whilst it is true that people wanting true designer gear are unlikely to be interested, the mass market are and hence this can be a succesful strategy. Remember traditionally as products move upmarket, and prices increase, the size of the market decreases in terms of numbers of consumers.