I'd say this is just a cynical ploy by Trump to rile up his base - and to raise funds, which he's already trying to do using this as an excuse. Even his own lawyer admits that they haven't heard anything from the Manhattan prosecutor's office.
The grand jury for this case hasn't even finished hearing witnesses yet. Even if they do recommend an indictment (which couldn't be before Monday at the very, very earliest, since they're scheduled to hear from a witness that day) there's nothing to say an arrest warrant would be issued immediately.
For instance, the Georgia grand jury (the one looking into Trump for electoral fraud) finished deliberations weeks ago and according to interviews given by jury members, they recommended multiple indictments but no arrest warrants have been issued yet.