Not really, but it's not worth arguing about. I really doubt this show is going to crossover.
Well, the President of the CW didn't completely rule it out when he was asked this. Taken at face value, I'd argue that it just means that while there are no current plans for a crossover, they haven't completely ruled out the possibility either.
More importantly, I don't see the harm in discussing the pros and cons of such an event irrespective of the above. And like everything in life, there are benefits and negatives to linking the iZombie TV-verse to the Arrow/Flash-verse. To pretend otherwise is to be deliberately close-minded.
Arguing that linking the two isn't - strictly speaking - necessary is a meaningless statement as that's not how television (or anything in life, really) operates. Was it necessary to place the Flash and Arrow in the same universe? No, but they did it anyway. Didn't introducing the Flash and superpowers create all sorts of plothole issues for Arrow? Yes, but the vast majority of viewers overlook them as part of the suspension of disbelief as they're needed in order to make the respective shows work.
In terms of negatives, the biggest one I can think of is that it unnecessarily commits the other two shows on how the universe's afterlife and undead work (presuming iZombie will have to go into that at some point; to explain Liv's current predicament). Should either the Flash or Arrow decide to go down this route at a later stage, the creators would find that creativity a little more restricted.
However, I feel the positives far outweigh this. People have argued that the show doesn't quite fit in with Arrow and the Flash as it's got a different feel and is in an entirely different genre. However, I think this is more a positive than a negative.
For starters, this allows the characters to do, explore and develop in ways that they wouldn't normally be able to in their respective shows. Much like how Arrow allowed The Flash's characters explore the more serious aspects of their superhero activies; while the Arrow characters got to show their more light-hearted side on The Flash. Likewise, Liv's need for eating brains would likely be explored more darkly on those shows rather than a quirky habit of hers, as it appears it will be done on her show (based on the trailer).
Another is that Liv has a completely different skill set than the other two. Meaning, crossovers allow the creators to do storylines that they would otherwise be unable to do. Likewise, there's more room for synergy between Olivia and the other two superheroes. For instance, having Flash or Arrow on iZombie would let the show tackle more physical threats while having Liv on theirs would let them tackle mysteries differently.
Lastly, it paves the way for a hilarious (in my humble opinion) piece of dark humour whenever Liv's brain-eating talents get brought up. I can just picture Cisco (from The Flash) excitedly raising the possibility of getting Liv to eat Barry's mother's brains to find clues as to her killer, only for the rest of Team Flash to go "What?! Hell no!!", Caitlin to logically point out that it's been too long and Barry's mother's brain would no longer be intact, and for the rest to pretend that was what they were thinking as well (and not because it's gross).
