According to the Columbia Guide to Standard American English (
www.bartleby.com/68/84/284.html)
“'all right' is the only spelling Standard English recognizes.”
This means “alright” is generally considered unacceptable in “educated”, formal English. However, you will probably continue to see it in magazines and on the Internet, and over time, it will possibly become acceptable, just like “altogether” (which started as 'all together' and “already” (which started as 'all ready').