The following MWE provides \hidecontent[<transparency>]{<stuff>} that hides <stuff> with a white transparent box. Optional transparency is set as <transparency> (provided by Heiko's transparent package); default is 0.25 or 25%:

\documentclass{beamer}% http://ctan.org/pkg/beamer
\usepackage{transparent}% http://ctan.org/pkg/transparent
\setbeamercovered{transparent}
\newcommand{\hidecontent}[2][0.25]{{% \hidecontent[<transparency>]{<stuff>}
\setbox9=\hbox{#2}% Store <stuff> in \box9 to obtain height/width
\transparent{#1}\ooalign{\usebox9\cr\color{white}\rule{\wd9}{\ht9}\cr}}}
\begin{document}
\begin{frame}[plain]
\begin{itemize}
\item<1> Current work 0
\item<2> Future works 1
\item<2> Future works 2
\begin{center}
\mbox{\only<1>{\includegraphics[scale=0.35]{example-image-a.pdf}}}%
\mbox{\only<2>{\hidecontent{\includegraphics[scale=0.35]{example-image-a.pdf}}}}%
\end{center}
\end{itemize}
\end{frame}
\end{document}
beamer doesn't adequately handle hiding of graphics, hence the use of \hidecontent. This works well with rectangular content. Other content (textual, for example), is best dealt with by beamer itself.