Will the HST rebates be paid each year after 2010 as well, or is this a one time thing?
Assuming you're referring to the provincial Ontario Sales Tax Transition Benefit, it is designed to be temporary only, and is directly related to the introduction of the HST in Ontario this July 1st, 2010. Refer:
As part of Ontario's new comprehensive tax package, the Ontario Sales Tax Transition Benefit (OSTTB) will provide temporary relief to residents of Ontario to help them adjust to the new harmonized sales tax system that comes into effect on July 1, 2010.
The transition cheques issued under the OSTTB are to be issued in: June 2010, December 2010, and June 2011. That's it. Those cheques will not be issued every year. See also the question Ontario special HST sales tax transition rebate cheques: When and how much?
If you're referring to, on the other hand, the benefit cheques that some people receive as a result of the GST/HST Credit (at the federal level), that program is designed to be ongoing. Here's a bit of information (or check the previous link):
The GST/HST Credit program issues payments to Canadians with low and modest incomes to help offset all or part of the GST/HST they pay on the purchase of goods and services. [...]
To receive the GST/HST credit, the recipient has to apply for it, even if it was received in the previous year. To apply, the recipient must file an Income Tax and Benefit return, even if there is no income to report. Eligible taxpayers may apply for the credits any time during the year in which they meet the requirements. [...]
The GST/HST credit is issued four times a year: January, April, July and October (generally the fifth day of the month) [...]