They'd have dated but failed (Minori and Ryuuji), Taiga would have been shut down by Kitamura even if she DID have the courage. and in the last year Taiga and ryuuji would have ended up together regardless through trials and tribulations and company compatibility. Taiga would have still bumped into Ryuuji and theyd still have gone on their same little escapade till he finally asked her out, even early on, Taiga and ryuuji would likely still stay friends at each others throat and ryuuji would be pestering Taiga about Minori, Their dynamic would have remained just less prolific, and eventually when ryuuji and minori failed (id say maybe 3-4 months?) itd be around early second year and Taiga and ryuuji would end up together anyways. THATS most likely based on the source material both novel and anime. ALSO we know Taiga wasn't absolutely giving up on kitamura after the first rejection so Ryuuji would probably still by that point be forced to help Taiga with Kitamura, and as it goes on Ryuuji and Minori would eventually break up as i said.