The revamp is expected to follow News International's move to new £600 million full-colour presses in March.
According to agency sources, the new presses will be the catalyst for changes that could include The Sunday Times going compact, moving to a seven-column grid and running with pull-out sections in the main paper instead of polybagged extras.
The Times on Saturday, which, like the weekday editions, is already compact, is expected to be used as a test for The Sunday Times following suit, one source said. This could involve moving sections of the Saturday Times package inside the main paper.
Agencies have expressed some concern over the move to full-colour owing to potential rate card increases.
A Times Media spokeswoman said: "This is gossip and speculation. The opportunity of full colour is allowing all editors to look at opportunities."