Answer
As long as they are separated by a short distance then yes, it will be fine. For example if you are using the new K.2 loudspeakers for your mains and KW or legacy K’s for your monitors, then this will work perfectly fine.
What is not recommended, however, is attempting to “array” K.2 loudspeakers alongside K or KW Series within close proximity. For broader coverage, two or more speakers may be splayed (aimed so that the horizontal coverage of the speakers has minimum overlap). For best results, this should always be done with identical speakers.