You can use the fwlw
("First Word, Last Word") package; a little example using a footer defined with the fancyhdr
package:
\documentclass{article}
\usepackage[latin]{babel}
\usepackage[a6paper,footskip=0pt]{geometry}
\usepackage{fwlw}
\usepackage{fancyhdr}
\usepackage[veryoldstyle]{kpfonts}
\usepackage{lipsum}
\fancyhf{}
\fancyfoot[R]{\usebox\NextWordBox}
\renewcommand\headrulewidth{0pt}
\pagestyle{fancy}
\begin{document}
\lipsum[4-60]
\end{document}
An image of the first four pages:

The package gives access to the first word on the current page (\FirstWordBox
), the first word on the next page (\NextWordBox
), and the last word on the current page (\LastWordBox
).
The package also offers a predefined page style NextWordFoot
to read ahead to the first word on the next page:
\documentclass{article}
\usepackage[latin]{babel}
\usepackage[a6paper,footskip=0pt]{geometry}
\usepackage{fwlw}
\usepackage[veryoldstyle]{kpfonts}
\usepackage{lipsum}
\pagestyle{NextWordFoot}
\begin{document}
\lipsum[4-60]
\end{document}

post_linebreak_filter
to analyze the paragraphs and thenatbegshi
to find the last line on the page and add the information you've got from step one. Easy ;-))