Very unlikely to be London again. 2014 was a collision of a number of factors that made the Excel Centre (just) affordable. London is just too expensive for the budget of a Worldcon without those factors. Hence why 79, 87 were in Brighton, 95, 05 and 24 in Glasgow. 57 and 65 were in London, but that was another age. Dublin is so far uncontested for 2029.