Assuming it is a revocable trust, the long term capital gains would apply immediately. A long term capital gain on an irrevocable trust depending on its terms would apply after a year or sooner depending on its terms.
A stepped up basis would not occur until your mother's death and depending on the amount of stock and the date of death there could be a limit on the stepped up basis.
I would suggest you contact an attorney before doing anything as the timing of the changes coud impact your mother's medicaid benefits in the future.
