The Warsaw theme of beamer uses the shadow outer theme which, in turn, is based on the split outer theme. The split outer theme sets the footline using the following template construction:
\defbeamertemplate*{footline}{split theme}
{%
\leavevmode%
\hbox{\begin{beamercolorbox}[wd=.5\paperwidth,ht=2.5ex,dp=1.125ex,leftskip=.3cm plus1fill,rightskip=.3cm]{author in head/foot}%
\usebeamerfont{author in head/foot}\insertshortauthor
\end{beamercolorbox}%
\begin{beamercolorbox}[wd=.5\paperwidth,ht=2.5ex,dp=1.125ex,leftskip=.3cm,rightskip=.3cm plus1fil]{title in head/foot}%
\usebeamerfont{title in head/foot}\insertshorttitle
\end{beamercolorbox}}%
\vskip0pt%
}
From the above it's clear that split's footline template creates the 50%-50% view you mention under Warsaw. Let's update this to suit your needs, now creating a 40%-40%-20% layout:

\documentclass{beamer}
\let\Tiny\tiny% http://tex.stackexchange.com/a/94159/5764
\usetheme{Warsaw}
%\usecolortheme{dolphin}% from Boadilla
\setbeamertemplate{footline}
{%
\leavevmode%
\hbox{\begin{beamercolorbox}[wd=.4\paperwidth,ht=2.5ex,dp=1.125ex,leftskip=.3cm plus1fill,rightskip=.3cm]{author in head/foot}%
\usebeamerfont{author in head/foot}\insertnameinstitute
\end{beamercolorbox}%
\begin{beamercolorbox}[wd=.4\paperwidth,ht=2.5ex,dp=1.125ex,leftskip=.3cm,rightskip=.3cm plus1fil]{title in head/foot}%
\usebeamerfont{title in head/foot}\inserttopic
\end{beamercolorbox}%
\begin{beamercolorbox}[wd=.2\paperwidth,ht=2.5ex,dp=1.125ex,leftskip=.3cm,rightskip=.3cm plus1fil]{author in head/foot}%
\usebeamerfont{title in head/foot}Page~\insertframenumber
\end{beamercolorbox}}%
\vskip0pt%
}
\newcommand{\insertnameinstitute}{\insertshortauthor, \insertshortinstitute}
\newcommand{\topic}[1]{\def\currenttopic{#1}}\topic{}
\newcommand{\inserttopic}{\currenttopic}
\author[A Author]{An Author}
\institute[Institute]{INSTITUTE}
\title[A title]{An interesting title}
\topic{Some topic}
\begin{document}
\begin{frame}
\maketitle
\end{frame}
\begin{frame}
\frametitle{foo}
\end{frame}
\end{document}
I am unfamiliar with your choice of the term topic, as there's no such definition in beamer that I know of. Instead, I created \topic{<topic>} that you can change on the fly throughout the presentation.