You can use a robotium condition to wait for the text to disappear. Here's a method I use for that.
private void waitForTextToDisappear(final String text, int wait) {
Condition textNotFound = new Condition() {
@Override
public boolean isSatisfied() {
return !solo.searchText(text);
}
};
assertTrue("Text gone: " + text, solo.waitForCondition(textNotFound, wait));
}