Wales failed to qualify for the 2018 World Cup in Russia just over a year after they reached the semi-finals of the 2016 European Championship with Coleman in charge.
The manager's current contract runs until next year and, despite achieving the Dragons' best international result to date, he is has been tipped to leave the Wales job before then.
'Now, there is a barren year for the Welsh lads and there will be 12 months of just playing friendlies and then they will be starting the next year for the European Championship after the World Cup', said Toshack, who managed the side between 2004 and 2010. 'So maybe if he was thinking of finishing after the World Cup it might just be that now is the right time to bring in a new man and give him that 12 months to prepare things'.
'The sell by date on managers these days has changed an awful lot from years ago', Toshack added. 'I know that Chris had one or two interesting offers nine, twelve months ago but things change very quickly in football managing'.