Sacks said that after Israel’s declaration of war on Hamas/Gaza in October 2023, the situation “could spiral out of control and become a regional war.” The normalized prediction frames this as a claim that there was a significant risk of a broader regional war involving multiple Middle Eastern countries.

What actually happened by late 2025:

• Lebanon/Hezbollah: Hezbollah opened a northern front on 8 October 2023, and cross‑border clashes escalated into what is widely described as an Israel–Hezbollah war, including an Israeli ground invasion of southern Lebanon in October 2024 and a U.S.- and France-brokered ceasefire on 27 November 2024.(dw.com) This clearly turned the Gaza war into a two‑front conflict involving Lebanon as a separate theater.
• Iran–Israel: In April 2024, Iran launched more than 300 drones and missiles directly at Israel in “Operation True Promise,” its first open state‑to‑state attack on Israel, widely characterized as an unprecedented escalation and spillover of the Gaza war; Israel carried out limited retaliatory strikes.(en.wikipedia.org)
• Yemen/Red Sea (Houthis) and Western powers: Yemen’s Iran‑backed Houthi movement attacked Red Sea shipping explicitly in support of Gaza, prompting repeated U.S.–U.K. air and naval strikes on Houthi targets from January 2024 onward and a larger U.S. campaign in Yemen in 2025; these actions are officially framed as part of the Red Sea crisis and the broader Middle Eastern crisis linked to the Gaza war.(commonslibrary.parliament.uk)

Taken together, the Gaza war clearly spread into multiple interconnected fronts (Gaza, Lebanon, direct Iran–Israel exchanges, Yemen/Red Sea, Iraq–Syria militia attacks on U.S. forces) involving several Middle Eastern states plus external powers. Many analysts and official documents explicitly describe this as a regional crisis or Middle Eastern crisis stemming from the Gaza war.(en.wikipedia.org)

However, whether this counts as the conflict having fully “spiraled out of control and become a regional war” is not clear-cut:

• The heaviest sustained ground fighting remained in Gaza and, for a period, southern Lebanon. Despite the Iran–Israel missile exchange and Red Sea hostilities, there has not been a long‑running, conventional multi‑state war on the scale of the 1967 or 1973 Arab–Israeli wars. Ceasefires and diplomacy repeatedly contained escalations (e.g., the November 2024 Israel–Hezbollah ceasefire; limited tit‑for‑tat strikes between Iran and Israel rather than open war).(dw.com)
• Sacks’ statement is about risk (“might,” “could”) rather than a firm forecast that a regional war would happen. Whether the ex post outcome (serious but still partially contained regional escalation) validates a claim about “significant risk” is inherently hard to judge from outcomes alone.

Because:

1. The war did partially regionalize, with multiple countries directly involved in fighting linked to the Gaza war, supporting the spirit of his warning; but
2. There has not been an uncontested, widely‑described, full‑scale regional war in the classic sense, and his claim concerned risk rather than a definite outcome,

it is not possible to categorize the prediction as clearly right or clearly wrong. The assessment therefore is ambiguous rather than definitively correct or incorrect.