There are all sorts of factors influence the viability of a BA operated lounge (cost of renting space in the terminal, subsidy from airport operator, volume of premium traffic, income from partner airlines/alliance members etc) so in the absence of further info, I wouldn't read too much into the closure of one short-haul lounge and the business case for maintaing long-haul lounges is much stronger in any event.

In an ideal world, BA would have its own operated lounge at almost every outstation so you consistency of product and brand presence at the airport, but financially, it's completely unrealistic.