He is a Bishop, and has been since the ordination which caused him to incur excommunication, and would remain a Bishop whether excommunicated or not. While excommunication has certain effects, it does not cause one to cease to be Catholic, so if one wanted to, one could call him a Catholic Bishop at any time since 1988. There is no “becoming” involved.
Whether he will become a fully functioning Catholic Bishop remains to be seen. The man is still suspended. Indeed, it is not even clear that he will remain a fully functioning Bishop within the context of the SSPX—