From a financial perspective, it makes no sense for BA to pursue this issue to its ultimate legal conclusion, irrespective of whether or not they believe they'll win. The costs almost certainly exceed any financial settlement they'd have to offer Unite/BASSA to resolve the matter well before then. Again, provided BA made a reasonable offer, then the Court will not entertain a case against them.
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I am a betting man, and I would take a big bet that this issue will not result in a precedent-setting Court decision.
I agree that BA almost certainly don't want the cost of taking this to court. however it is to be remembered that BA have good in-house lawyers (I've worked with them over the years) who will do most the work. The question that is more interesting is how long can BASSA/UNITE financially support the legal action? Especially if their funds are drained by other strike action across the public sector.
So yes I would expect this to be settled before it got to the final day in court, but that will probably be due to BASSA/UNITE needing to save funds/running out of funds, and so accepting pretty much any settlement from BA. Especially is BA ensure the day in court is pushed out 2/3 or more years.
I also see that some people think that victory in court would be a huge win. But to settle out of court in 3 years, would be a very hollow victory, and even then the court is highly unlikely to enforce the return of ST with seniority (return of ST maybe, but the seniority highly unlikely). By then BA is likely to have returned it anyway. But I also see that this is not a clear cut (either way) case. Imagine also the affect if UNITE/BASSA were to refuse all settlement offers and then LOSE in court in 2/3 time, and then have BA's costs to pay, even if they only get 50% of the costs awarded against them. They have a lot more to lose in a long drawn out court case.