To be sure this is much more hackish of a solution than Barry’s and would take more maintenance, but you could execute the javascript below to manually click the component’s refresh button. Simply add it as an after requery action on the model. Keep in mind if you have multiple chatter feeds on the page this will refresh all of them. Ths syntax is subject to change due to its reliance of element names which are subject to change by Salesforce.
$ = skuid.$;<br />$("[data-value='Most Recent Activity']").click();
