Statement: The last chapter of part 1 and before Kakashi Gaiden with Hinata seeing Naruto send off may have been a sign that Kishi was planning on NaruHina if only Sakura doesn't rise to popularity. In other words, he have placed it on standby until the call was right. Once Sakura's push was deemed as a failure, Hinata will start her shine as well as NaruHina being the now love interest focus.
Agree or disagree?
I disagree, mainly because I don't think they thought that far ahead in terms of the pairings. I've always seen Hinata as a character to spotlight Naruto as the MC a little more by the use of her feelings. She's someone to show that Naruto is also appreciated by the opposite sex, not just Sasuke.
That chapter was to show how all the rookies decide to become stronger. With Hinata being shown last due to the entirety of her character revolving around Naruto as her inspiration. Once again using her to spotlight Naruto's importance as an MC. The only actual relationship tease in that chapter was a ShikaTema moment with Temari literally teasing Shikamaru. However, we're also shown panels of Ino appreciating Choji, Tenten admiring Lee and Kiba teasing Hinata but we know none of that led anywhere.
So no, I don't think they were worrying about the pairings all that much back then at all. If they were then NH would've had more moments in the entirety of the manga so as to be able to shift to that relationship with less backlash had NS not worked out.