Beancounters over at IHS iSuppli increased their iPad sales forecast on Wednesday, citing HP’s TouchPad debacle and Apple’s decreasing supply issues as the main reasons behind their new assessment.

The outfit now forecasts Apple will manage to sell 44.2 million iPads in 2011, up from a previous estimate of 43.7 million. Overall tablet sales estimated were also revised upward, from 58.9 million to 60 million.

iSuppli sees the tablet market as a one horse race and applauds Apple’s resilience to supply issues and its streamlined production process.

However, by 2014 iPad momentum is expected to weaken as Windows 8 enters the fray. Still, by 2015 iSuppli forecasts Apple will still account for about 44 percent of the tablet market.