According to Swype's advanced tips page:
Switching languages: To switch between the two most recent languages, Swype from the Swype-key to the key with the language initials on it.
Since I updated Swype, the language initials are on the space bar and this tip doesn't work any more. I can still switch languages by long-pressing the space bar but that's a hassle. What's the new quick way to change the language?
Here's a screenshot of the keyboard as it looks like for me: