What is the average time table to boosting SEO rankings through a complete website frontend+backend refresh?

[NikeFire]

I am hoping someone who encountered a similar situation can help out. Here are the general details.

Our company website is being rebuilt from the ground up - new copy, new information architecture, new theme, ideal URLs, data-driven research on search queries and keywords with an inbound marketing emphasis, CDN, the whole nine yards - as for several years under old management there was little emphasis on beating competition in the search results, or really on any of the fundamentals that matter. The only thing that cannot be reset, and will need to be tackled over time, is a link profile audit and weeding out the bad backlinks accrued over a decade.

We are in a very small niche, and even with impeded website design, copy, content and misaligned architecture, we are still somewhat competitive vis-a-vis our competitors, just not top-3 triangle competitive for the terms that really matter. In addition, nearly all of our competitors do not (or at least do not appear to) optimize for SEO and UX, they just happened to choose to include terms in the copy that prospects would use when searching, rather than worrying about the semantics of branding (as in our old management's iron clad preference).

Can someone here give an indication of when we would see rankings begin to improve in the search engine results pages upon completion and deployment of the new website? I understand I could be looking at up to a 6-month window, but I am looking for a definitive answer to tell my bosses, who may be expecting an immediate boost in the rankings.

[JordanLowry]

I dont think there is a hard and fast rule for this. I have noticed ranking increases and page traffic after building out additional directories within a site. It took around a week or so to get indexed and begin ranking within the serps and drive traffic back to the site. This was a site with a modest domain authority. I think it depends on a variety of factors. One thing id recommend is track all the keywords you hope to rank for and keep an eye on the indexation of your site.