What they've done with the Lana arc has destroyed the credibility of Lois/Clark. If I was dating someone and they pulled that shit on me I'd never speak to them again.
But Clark and Lois weren't dating. They were just beginning to notice that there was an attraction between them, and were on the verge of a first kiss when Lana showed up.
For Clark to suddenly do a 180 and decide that Lois is the love of his life does not indicate maturity, it indicates an emotional adolescent whose feelings are all over the place.
This is speculating ahead of the evidence. Why assume there will be anything sudden about it? Why assume the producers of this show actually intend to make Lois and Clark an actual couple during the run of this series, or at least this season? It's a well-known trope that when a series is built around Unresolved Sexual Tension between the leads, it can be fatal to actually make them a couple. Countless shows have followed the pattern of keeping the potential couple at arm's length, always drawn to each other but never acting on it. Whenever such a couple is on the verge of admitting their love, something happens that pushes them apart and prolongs the unresolved tension. It's part of the basic UST formula. Moreover, it makes sense within the context of the Superman mythos. Lois Lane is suposed to be the love of Clark/Superman's life. If that relationship actually gets consummated during
Smallville, then the story is over -- where do you go from there?
So I'm convinced that's what this whole Lana arc was about -- not only giving that character better closure, but justifying an indefinite postponement of Lois/Clark. Clark won't be ready to love anyone else for quite a while, and Lois will be too upset about his rejection to pursue him. So they'll go back to keeping their distance, at least until the end of the season.
They didn't do a thing to wrap up Clana in terms of the previous 7 seasons. Clark is still madly in love with her, nothing is wrapped up, nothing is changed, she is just disappeared again for the umteenth time, this is just something we have seen before, and Bizarro could just as easily resurface next week and suck the kryptonite out of her.
Sure, something could be contrived to cancel out the kryptonite, but it's a gross misreading of the writers' intent to assume that's what they want. This whole season under the new showrunners has been about Clark getting rid of baggage from his past and finally beginning to grow into the man we know he'll be. And he couldn't really be free to do that unless the overriding issue of his past life, his relationship with Lana Lang, was brought to a decisive conclusion. Everything the writers have done this year has been about Clark letting go of his old patterns and moving forward. They've been aggressively repudiating the policies of the old showrunners. Listen carefully and you can hear them putting their frustrations with the old order into the characters' mouths -- having people say how refreshing and overdue it is for Clark to get out of his self-absorption and begin being a hero, having Lana say how much she's changed for the better in her time away, etc. The last thing they'd want to do is go back to the old Clark-Lana holding pattern. This story arc was about
ending Clark-Lana permanently, but doing so in a way that served the Lana character well rather than just discarding her or killing her, and in a way that reaffirmed Clark's growth toward his heroic destiny. (If she'd died as a result of her involvement in his life, it could've turned him against being a hero. Now, with her embracing heroism herself, he's honoring her by doing the same.)