As far as I can recall, there was no announcement of disbandment at that time.
Since 1968 (and its properly-announced split), there had been several intermittent periods of operation of "The Shadows", interspersed with "Marvin, Welch & Farrar* and "Marvin & Farrar", mainly:
(a) 1969 - the UK and Japan tours with Alan Hawkshaw (with a live LP being recorded)
(b) 1970 - the "Shades of Rock" LP
(c) 1973 / 1974 - the recording of "Rockin' With Curly Leads" and some subsequent promotion
(d) 1975 - Eurovision and the somewhat Euro-connected "Specs Appeal" LP.
An interview with Hank (published January 1976 but clearly conducted a few months earlier) gave no hint of any decision to disband The Shadows again, though there was no clear view of how things might progress.
The group issued only one track during 1976 and it was "20 Golden Greats" which changed the landscape for them. Had that not happened...