Ending the Season now makes no sense

Senna is out for just a week, why not give us the time to play her? Prior to Senna release, I was trying to climb as Soraka support, but my teams were trolling me too hard, and you can't really carry as Soraka, if the team is trolling. So instead of climbing, I actually dropped to Silver 4. Now, with Senna release, I'm climbing again. I got a 67% winrate with Senna support, over 50 games, and a lvl 7 Mastery. Although she clearly needs some buffs (the damage is underwhelming for an ADC, even with 6 expensive items), I can actually carry, because if my ADC is trash, I can become the ADC for my team and win anyway, and if my ADC is OK, we can hardstomp the bot against anyone. I got up 2 divisions by only spamming Senna, even though I had to lose huge amounts of LP when dodging because Senna was banned. I really feel like if the season lasted for 1 more month, I could reach Gold easy. Why give us just 1 week of Senna? We need more time to play the champion and a chance to climb