How plausible is it to climb from gold 4 to plat 5 before season end?

no

If you can still have fun while playing go for it. If it actually stresses you out dont do it, not worth. Also gold border looks better than plat imo ^^

if youve played norms at a plat level then it might be ok. if youve been to plat before it should be pretty easy. if the highest youve ever been is gold 4 and you were trying when in gold 4 then it might be hard without a huge change in tinking or massive mechanic changes or roles changes which are likely to take more than a couple weeks. however, if you only have 50 games played and are gold 4 then playing 100 more games can certainly get you to plat even if youve never been there before.