You should be ok to SWITCH (not renew!) to Tier 1 General as long as you are in the UK and still meet the requirements at the time you apply. The tricky bit will be whether going from PSW to General will count as an extension or an initial application, because the requirements will be different from April for these two situations. If it counts as an extension, you'll be ok with the current bachelor's degree and salary level, but if it counts as initial, you have to have a masters and £20,000 salary to qualify. Perhaps Garry can comment?