I would not hold my breath.
The current flurry of articles in UK media is based on the fact that
UK news outlet I News, on November 8, 2022, published an interview-based article with Spanish Tourism Secretary Fernando Valdés. The minister was in London for the World Travel Market 2022 event. The article is behind a paywall. The usually well informed Spanish website
The Local ES provides some background:
“It is in Spain’s interest to get rid of the rule” and “lobby to convince [the EU] we can try to work an exception with them,” he is quoted as saying. Brexit news outlets the Daily Express and GB News have jumped on the story with headlines such as “Desperate Spain begs EU…”, which evidences how the ‘they need us more than them’ rhetoric is still alive for some.
I've quoted this not in order to start a discussion but to provide some context because some of the news media who have picked this up from other news media make it sound as if such a change of rules is imminent and it will be a unilateral measure taken by Spain. This is not the case.
According to The Local ES, some areas of Spain such as Valencia have been lobbying the national Spanish government since last year to exempt Britons from the 90-day rule, mainly because of the numerous Britons who own holiday homes there or who want to stay for up to 6 months in one go (especially pensioners of all nationalities btw). The Local ES article also addresses bilateral agreements. Spain has old bilateral agreements with 19 non-EU countries that had been signed in the 1960s or earlier but the UK is not among them and it is legally not possible to conclude new bilateral agreements of this sort.
As Spain’s Tourism Secretary pointed out regarding changing the rules “we cannot do so unilaterally” and “the solution must come from them”, meaning the EU.
In my albeit limited experience, the law-making mills of the EU grind very very slowly.