Hi guys,
The planned release dates for 4.3 and 4.2.2 are July, 2009 and June, 2009. You can see up to date information on upcoming X-Cart versions and release dates on our website:
http://www.x-cart.com/roadmap.html
If the patch is ready before the planned release dates, we will publish it here. As far as I understand the only thing that needs to be changed is the URL where X-Cart sends Protx/SagePay payment transactions.
Best regards,