I get the feeling that shopping centres contract the supply, management and maintenance of these kiddy rides to an external company that specialises in these machines on a lease agreement rather than buy them outright. The rides would more likely be taken back by this company and refit with a new shell and livery to meet current trends as the 'engine' of the ride is pretty simple and can be easily rebuilt/repurposed.
The old shells probably become landfill (or end up on ebay) but you could call such a company to see what they do with them.