To start with, the spec sheet for the device shows a max sample rate of 2.86 MS/sec for single-channel analog output. It lowers as you add more output channels, though not proportionally.
The next consideration is the # of samples per sine wave cycle. Too few makes a waveform that isn't very sine-like. I would generally aim for at least 20, though that still isn't especially smooth.
Finally, you need to figure out whether you will regenerate the same wave over and over or whether you will change it on the fly. If the latter, you need to account for the need to calculate and feed the task buffer with fresh data at your sample rate (on average).
With a 6363 type device, I'd venture you could regenerate a decent sine wave of up to about 100-150 kHz. That kind of ballpark.
-Kevin P
CAUTION! New LabVIEW adopters -- it's too late for me, but you *can* save yourself. The new subscription policy for LabVIEW puts NI's hand in your wallet for the rest of your working life. Are you sure you're *that* dedicated to LabVIEW? (Summary of my reasons in this post, part of a voluminous thread of mostly complaints starting here).