By selling after the budget would mean the capital gain would be at the new budget rate unless they permit pro-rating gains over the period the gain was realized (which I doubt would be the case).  I would speculate most selling of gainers would be before the budget is released to lock in gains at 50% and selling losers after the budget if the rate is increased to have the losses at 75% (assuming that is the new inclusion rate).  Then buying back in, keeping in mind to wait long enough to ensure the loss is not considered superficial for tax purposes.